1. Field of the Invention
The present invention relates to a steam environmentally generated drainage system and method for use in connection with producing hydrocarbons from a formation or reservoir using in situ steam generation and gravity drainage.
2. Description of the Prior Art
The use of steam assisted gravity drainage (SAGD) systems is known in the prior art. Hydrocarbons obtained from subterranean formations are often used as energy resources, as feedstocks, and as consumer products. It is an important issue to develop more efficient recovery, processing and/or use of available hydrocarbon resources, while increasing safety to personnel and protecting the surrounding environment. In situ processes may be used to remove hydrocarbon materials, such as bitumen, from subterranean formations that were previously inaccessible and/or too expensive to extract using available methods. To efficiently and effectively extract hydrocarbon material from subterranean formations, the chemical and/or physical properties of the hydrocarbon material may need to be altered to allow the hydrocarbon material to be more easily flow through the formation. The systems and methods associated with these changes may include in situ reactions that produce removable fluids, composition changes, solubility changes, density changes, phase changes, and/or viscosity changes of the hydrocarbon material in the formation.
It is known that deposits of heavy hydrocarbons contained in relatively permeable formations (for example in oil sands) are found throughout the world, and these deposits can be surface-mined and upgraded to lighter hydrocarbons. Surface mining and upgrading oil sands is an expensive process with questionable environmental impact and human health safety.
Alternatively to surface mining, an in situ heat treatment process may be used to change the heavy hydrocarbons into a more mobile material for recovery. This in situ heat treatment process may include the use of vertical and/or substantially vertical wells, horizontal or substantially horizontal wells (such as J-shaped wells and/or L-shaped wells), and/or u-shaped wells are used to treat the formation and produce the mobile oil. In some embodiments, combinations of horizontal wells, vertical wells, and/or other combinations are used to treat the formation. In certain embodiments, wells extend through the overburden of the formation to a hydrocarbon containing layer of the formation. In some situations, heat in the wells is lost to the overburden. In additional situations, surface and overburden infrastructures used to support heaters and/or production equipment in horizontal wellbores or u-shaped wellbores are large in size and/or numerous.
The use of in situ heating using injected steam has raised questions towards the damages to the environment and the safety to the surrounding populations and personnel working on site. Currently, SAGD projects generate steam at surface using steam generators or boilers. These projects burn primarily natural gas to generate the steam and emit the combustion gases to the environment containing wasted heat, wasted water vapor, carbon dioxide, nitrogen oxides, sulfur oxides and other pollutants. Additional energy and steam are wasted in the equipment used to generate and transport the steam to the reservoir. They also must generate boiler quality feed water for steam generation. This requires significant amounts of make-up water and the disposal of wasted blowdown water. Consequently, by generating steam at surface, SAGD projects waste energy and water; emits carbon dioxides and other pollutants to the environment; and require significant amounts of capital and operating expenditures.
Therefore, a need exists for a new and improved steam environmentally generated drainage system and method that can be used for producing hydrocarbons from a formation using in situ steam generation and gravity drainage. In this regard, the present invention substantially fulfills this need. In this respect, the steam environmentally generated drainage system and method according to the present invention substantially departs from the conventional concepts and designs of the prior art, and in doing so provides an apparatus primarily developed for the purpose of producing hydrocarbons from a formation using in situ steam generation and gravity drainage.